my sick betta fish

Question
QUESTION: My poor little guy...I feel so bad for him.  about a week and a half ago I was out of town and my husband, who was home, said Nemo wasn't eating. When I got back I did a full water change (it's only a 1 gallon tank). I noticed he was staying at the bottom of the tank most of the time. I decided to put his tall artificial plant back in the tank. He seemed to like it because almost ever since he's been sitting on top of it. He hardly moves, doesn't eat, his fins are clamped almost all the time. I haven't noticed any waste since I changed the water but he hasn't been eating either. so I don't know if he's constipated or just not interested in his food because of something else. I've been reading online about betta diseases and his symptoms seem to match swim bladder. he seems to sink when he tries to swim and I've even noticed his body in a zigzag shape while sitting atop the plant. He sits at the top so he can get air readily but now I'm noticing that he seems to be breathing rapidly out of one gill and doesn't use his fin by that gill very much. His gill doesn't look red but the cover kind of looks wavy. I'm going to change his water again today but I just feel helpless. any insight please???
thank you!

ANSWER: Hello Jacci,
I'm sorry about your betta. How often are you doing water changes? With a one gallon tank, you need to completely change out his water at least once a week. What is the temperature in his bowl? He needs to stay rather warm, being that he is a tropical fish. Between 75 and 85 degrees Fahrenheit is best. Also, make sure you are feeding strictly betta food, and that you always use tap water conditioner.
Get some aquarium salt to put in his tank - he only needs a few grains each time after you change out the water. This will put electrolytes back into the water, which may help him recover faster.
Give him a very small amount of crushed, shelled pea and if he does have SBD, that will help him to digest.

---------- FOLLOW-UP ----------

QUESTION: Thank you for your response. I do strictly feed him betta food. I was doing full water changes once every 1-2 wks so I'll make sure I do it atleast once a week now. I use spring water. Do you think using tap with WC is better? I live in Florida so I don't use a thermometer; It gets up to 81 degrees in my home during the day and then at night 72 is the lowest this time of year and his tank is not near a window. Do you think that's okay?  
Thank you Brittany!
Jacci

Answer
Sudden temperature changes can have very bad effects on fish. As long as his temperature changes gradually throughout the day it should be fine.
As far as water goes, if you are using spring water it may or may not be okay. Tap water tends to have more minerals in it than spring water.